The Mass Spectrometry (MS) Facility Core has been established to maintain and provide the mass spectrometric and associated analytical capabilities required to support environmental health-related research conducted by EHS Center investigators, program project grant investigators, and pilot project investigators. This Core maintains state-of-the-art sample preparation and instrumental techniques that increase the sensitivity, mass range, specificity, and data processing capacity of the Core's analytical capabilities and the necessary databases for protein and organic compound identifications. In addition, this Core serves as an educational resource by providing an interdisciplinary environment in which graduate students in chemistry, biochemistry, and toxicology pursue their thesis research. The facility provides a wealth of experience in the analysis of samples as well as in the interpretation of experimental data. Finally, the facility supports the development and implementation of new mass spectrometer configurations that will advance the analysis of environmental agents as well as proteomics.